Internal combustion engine

The invention and development of the internal combustion engine in the nineteenth century has had a profound impact on human life. The internal combustion engine offers a relatively small, lightweight source for the amount of power it produces. Harnessing that power has made possible practical machines ranging from the smallest model airplane to the largest truck. Electricity is often generated by internal combustion engines. Lawnmowers, chainsaws, and generators also may use internal combustion engines. An important device based on the internal combustion engine is the automobile .

In all internal combustion engines, however, the basic principles remain the same. Fuel is burned inside a chamber, usually a cylinder. The energy created by the combustion, or burning, of the fuel is used to propel a device, usually a piston, through the chamber. By attaching the piston to a shaft outside of the chamber, the movement and force of the piston can be converted to other movements.

Principles

Combustion is the burning of fuel. When fuel is burned it gives off energy, in the form of heat , which creates the expansion of gas. This expansion can be rapid and powerful. The force and movement of the expansion of gas can be used to push an object. Shaking a can of soda is a way to see what happens when gas expands. The shaking motion causes a reaction of carbon dioxide—the soda's fizz—which, when the can is opened, pushes the soda's liquid from the can.

Simply burning fuel, however, is not very useful for creating motion. Lighting a match, for example, burns the oxygen in the air around it, but the heat raised is lost in all directions, and therefore gives a very weak push. In order for the expansion of gas caused by combustion to be made useful, it must occur in a confined space. This space can channel, or direct the movement of the expansion; it can also increase its force.

A cylinder is a useful space for channeling the force of combustion. The round inside of the cylinder allows gases to flow easily, and also acts to increase the strength of the movement of the gases. The circular movement of the gases can also assist in pulling air and vapors into the cylinder, or force them out again. A rocket is a simple example of the use of internal combustion within a cylinder. In a rocket, the bottom end of the cylinder is open. When the fuel inside the cylinder explodes, gases expand rapidly toward the opening, giving the push needed to force the rocket from the ground.

This force can be even more useful. It can be made to push …